While substantial effort and attention continues toward the development of newer and more sustainable energy supplies, the conservation of energy by increased energy efficiency remains crucial to the world's energy future. According to an October 2010 report from the U.S. Department of Energy, heating and cooling account for 56% of the energy use in a typical U.S. home, making it the largest energy expense for most homes. Along with improvements in the physical plant associated with home heating and cooling (e.g., improved insulation, higher efficiency furnaces), substantial increases in energy efficiency can be achieved by better control and regulation of home heating and cooling equipment. By activating heating, ventilation, and air conditioning (HVAC) equipment for judiciously selected time intervals and carefully chosen operating levels, substantial energy can be saved while at the same time keeping the living space suitably comfortable for its occupants.
Historically, however, most known HVAC thermostatic control systems have tended to fall into one of two opposing categories, neither of which is believed be optimal in most practical home environments. In a first category are many simple, non-programmable home thermostats, each typically consisting of a single mechanical or electrical dial for setting a desired temperature and a single HEAT-FAN-OFF-AC switch. While being easy to use for even the most unsophisticated occupant, any energy-saving control activity, such as adjusting the nighttime temperature or turning off all heating/cooling just before departing the home, must be performed manually by the user. As such, substantial energy-saving opportunities are often missed for all but the most vigilant users. Moreover, more advanced energy-saving settings are not provided, such as the ability to specify a custom temperature swing, i.e., the difference between the desired set temperature and actual current temperature (such as 1 to 3 degrees) required to trigger turn-on of the heating/cooling unit.
In a second category, on the other hand, are many programmable thermostats, which have become more prevalent in recent years in view of Energy Star (US) and TCO (Europe) standards, and which have progressed considerably in the number of different settings for an HVAC system that can be individually manipulated. Unfortunately, however, users are often intimidated by a dizzying array of switches and controls laid out in various configurations on the face of the thermostat or behind a panel door on the thermostat, and seldom adjust the manufacturer defaults to optimize their own energy usage. Thus, even though the installed programmable thermostats in a large number of homes are technologically capable of operating the HVAC equipment with energy-saving profiles, it is often the case that only the one-size-fits-all manufacturer default profiles are ever implemented in a large number of homes. Indeed, in an unfortunately large number of cases, a home user may permanently operate the unit in a “temporary” or “hold” mode, manually manipulating the displayed set temperature as if the unit were a simple, non-programmable thermostat. Thus, there is a need for a thermostat having an improved user interface that is simple, intuitive and easy to use such that the typical user is able to access many of the features such as programming energy-saving profiles.
At a more general level, because of the fact that human beings must inevitably be involved, there is a tension that arises between (i) the amount of energy-saving sophistication that can be offered by an HVAC control system, and (ii) the extent to which that energy-saving sophistication can be put to practical, everyday use in a large number of homes. Similar issues arise in the context of multi-unit apartment buildings, hotels, retail stores, office buildings, industrial buildings, and more generally any living space or work space having one or more HVAC systems.
Some attempts have been made to make programming of programmable thermostat more appealing to greater numbers of users. For example, U.S. Pat. Nos. 7,181,317 and 7,634,504 discuss methods for programming configuration information for thermostats wherein a series of interview questions are asked to a user. The user responses to the questions are stored and one or more schedule parameters can be modified based on the user responses. It is believed, however, that such approaches rely heavily or entirely on the user's answers, and as a result will be either wasteful of energy and/or unnecessarily subject the occupants to uncomfortable temperatures when people make mistakes when enter their responses to the questions.
U.S. Pat. No. 7,784,704 discusses a self-programmable thermostat that initially appears to function as an ordinary manual thermostat. The thermostat privately observes and learns a user's manual temperature setting habits and eventually programs itself accordingly. The thermostat looks for patterns, such as three similar manual overrides on consecutive days. Manual set point changes override current programmed set point temperatures. It is believed, however, that further improvement can be made in discussed method's ability to generate energy efficient program schedules.